The invention relates to a touch device interface. By way of example, the inventive touch device interface can be used as a user-input section of a touch screen interface. Although a touch screen appears to be a unitary piece of hardware, it actually comprises an output device, namely a display or screen, and an input device which is sensitive to touching or approaching the surface of the display with a finger or stylus. Touch screens can be implemented by organizing an x-y matrix of infrared rays over the screen, in which case touching the display surface is not necessary. Alternatively the screen can be overlaid by a transparent pressure-sensitive switch matrix which is scanned in substantially similarly to the way electronic keyboard matrices are scanned. The layout of the switch matrix may resemble that of a general-purpose typewriter, or the layout may be dedicated to specific purposes or applications. Touch screen interfaces are frequently used in connection with laptop or palmtop computers, personal digital assistants (“PDA”), remote control devices, digital cameras, navigators, entertainment devices, and many other types of devices.
A problem with conventional touch screen interfaces is that the user of the touch screen interface must be able to see the layout of the switch matrix in order to be able to select a specific key to be activated (“pushed”). Seeing the layout of the switch matrix is not always possible or easy, and visually impaired persons are a prime example. Even in cases wherein the user could see the switch matrix layout, looking at the switch matrix layout may disturb the user, such as the driver of a car.